How is most of the forces occurring around us related to electromagnetism? Here is an extract from my textbook-

Most of the phenomena occurring around us can be described under electromagnetism. Virtually every force that we can think of like friction, chemical force between atoms holding matter together, and even the forces describing processes occuring in cells of living organisms, have its own origin in electromagnetic force.

So, how are these forces related to that electromagnetic force and how do they have origin in it?
 A: In physics, There are four fundamental forces of nature which give a rise to other phenomenological force, for example, friction. Such forces are commonly encountered in everyday physics and are approximately described by empirical equations because the concept of force is meaningful only if one knows how to solve problems involving forces.
The
phenomenological forces, such as friction, the contact
force, and the viscous force, can be described by relatively simple
empirical mathematical expressions, but when examined in detail they
can be explained as the macroscopic manifestation of complicated interatomic
forces.
The four fundamental forces are the gravitational and electromagnetic interactions, which produce significant long-range forces whose effects can be seen directly in everyday life, and the strong and weak interactions, which produce forces at minuscule, subatomic distances and govern nuclear interactions. Some scientists hypothesize that a fifth force might exist, but these hypotheses remain speculative.

how do these forces are related to that electromagnetic force and how do they have origin in it?

Let's talk of normal force as friction is much harder to examine at the microscopic level (see here for more):
The origin of the normal force is similar to the origin of tension in a
string. When we put a book on a table, the molecules of the book exert
downward forces on the molecules of the table. The tabletop moves
downward until the repulsion of the molecules in the table balances
the force applied by the book. The more rigid the surface, the smaller
the deflection. Because no surface is perfectly rigid, compression always
occurs. However, the compression is usually too slight to notice
and for most purposes, we can assume ideal surfaces that are perfectly
rigid.
In equilibrium, the normal force $N$ exerted on a body by a surface is
equal and opposite to the resultant of all other forces that act on the body
in the perpendicular direction.

Edit: Intermolecular forces are the forces that mediate the interaction between atoms, including forces of attraction or repulsion (electromagnetic forces)  which act between atoms and other types of neighboring particles, e.g. atoms or ions.
